The present invention relates to a duct type charge eliminator for elimination of electric charge carried by charged materials, such as dust particles, granular particles, grains, low conductivity liquids, etc., strongly charged by friction in the course of conveyance through a pipe or duct. The duct type charge eliminator of the invention may be connected to the pipeline or duct for conveying these materials, so that the charge of such materials may be quickly neutralized by passing through said charge eliminator.
It is well known that various kinds of high resistivity powders, such as, for example, resin powders to be used for electrostatic powder coating, resin pellets, grains, ceramic powders, and also a number of low conductivity liquids, such as, for example, pure hydrocarbon liquids, fuels, etc., are highly charged during the course of transport through a pipe-line or duct. As a result, these strongly charged materials often cause a fire or explosion in the tank at the terminal of the pipe-line or duct due to the ignition induced by a spark produced by the electric charge of said materials. In other cases, the strongly charged powders or pellets deposit on the inner wall of the pipe-line or duct, as a result of the electrostatic attractive force and disturb the transport of the material. The reentrained flakes often produce a degradation of the finished coat of the powder coating.
However, there has been no charge eliminating apparatus to be used in the pipe-line or duct, and the only possible countermeasure for the aforedescribed charge-induced hazards or nuisance has been to use the conventional type charge eliminator at the outlet of the pipe-line. This often produced poor elimination performance, and a high cost of charge elimination. In many cases, it was almost impossible to attach the charge eliminator at the outlet of the pipe-line because of space limitation, the construction of the tank, safety problems of the tank, etc.